Machine for producing stacks of folded sheets of paper and method therefor

ABSTRACT

Machine ( 1 ) for converting paper comprising a starwheel unit ( 10 ) equipped with at least one cylindrical body having a plurality of grooves ( 15 ), each of which is configured to receive a respective sheet ( 11 ) of a plurality of folded sheets ( 11 ) that are carried in turn, for example between two transmission belts ( 200, 201 ), along a feeding direction ( 101 ), for example a direction substantially tangential to the starwheel unit ( 10 ). The starwheel unit rotates about a rotation axis ( 110 ), for example in a counterclockwise direction, and discharges in turn the sheets ( 11 ) present in the grooves ( 15 ) onto a formation table ( 20, 120 ). More precisely, the folded sheets are discharged to achieve a predetermined angular release position, in order to form a stack ( 50 ) of folded sheets ( 11 ). The machine ( 1 ) can comprise a transfer means for transferring the formed stacks ( 50 ) from the table ( 20, 120 ) to said conveying means ( 30 ). The transfer means comprises a rotation means ( 60 ) arranged to transfer the stack ( 50 ) of folded sheets ( 11 ) from the table ( 20 ) to the conveying means ( 30 ) through a rotation of a predetermined angle.

FIELD OF THE INVENTION

The present invention relates to the field of converting paper andsimilar products for making paper material in packages of folded sheetsstarting from web material.

In particular, the invention relates to a machine for making stacks offolded paper sheets, or similar products.

Furthermore, the invention relates to a method for making stacks offolded sheets.

BACKGROUND OF THE INVENTION

As well known, different types of machines and processes exist forobtaining stacks of folded paper sheets, or similar material, such astissue paper, napkins, or similar articles.

A type of such machines has a transfer roller capable of rotating aboutan axis and peripherally provided with a predetermined number of curvedblades. The blades extend starting from the roller in a direction whichis opposite to the roller rotation direction and impart to the rollersame a particular “star” shape from which the common name of “starwheel”derives.

Between two following curved blades the transfer roller is, therefore,equipped with a groove in which a feeding mechanism introduces in turn asheet of a plurality of sheets already folded and fed in quicksuccession. The rotating transfer roller transfers the fed folded sheetsinto the grooves from a feeding position to an discharge position. Inthe discharge position a barrier is provided that causes the sheets toexit from the respective grooves, in such a way to accumulate the sheetson a formation table where a stack of overlapped sheets is formed. Thedifferent arrangement of the barrier can cause the products to bestacked along a vertical axis, onto one another, or along a horizontalaxis, with the napkins leaning at an edge one after the other.

Once a predetermined height or length of the stack is achieved, underthe starwheel unit, separators operate for separating the last sheet ofthe already finished stack from the first sheet of the successive stack.In case of vertical stacking, once the separation of two sheets iscarried out, the table translates leaving the axis of the stack, whichis located on it, substantially vertical up to arrange the stack on aconveyor belt. In case of horizontal stacking, the products can bedirectly released on a conveyor belt or other conveyor.

An example of this kind of machine with stacking along a vertical axisis disclosed in EP1421021. In this case for increasing the productionrate, several coaxial starwheel units are provided that work inparallel. Each starwheel unit is associated to a conveyor belt to itdedicated on which the production of the stack of sheets is made. Moreprecisely, each of parallel conveyors, one for each starwheel unit andhaving a conveying direction that is orthogonal to the axis of thestarwheel unit, works discontinuously, i.e. during the transfer of theformed stack of sheets it remains still, whereas once transferred thestack, while the successive stack is forming, it shifts to a positionfor receiving a successive stack.

In both cases each stack of sheets has to be conveyed forward up to abanding station, or packaging station, where the stack is pressed andwound by a film of plastic material forming a pack. During the movementbetween the point in which the stack is released from the table onto theconveyor belt and the packaging station, the conveying direction of thestack is subjected to many variations, even sudden variations, which candamage the product and oblige to complicated technical solutions.

Therefore, in order to move the stacks of sheets, for example forfeeding them to a banding section, it is necessary to start fromdifferent adjacent lines of stacks that are present on the abovedescribed conveyors which are parallel to each other, and bring them toa configuration, in which they are arranged in column on a single row.To obtain this configuration, a further conveyor belt is providedarranged orthogonally to the above described conveyors on which theproduction of the line is carried out, as described in IT2006BO00801 orIT2001RE00121.

A relevant and known drawback of the stacking machines of sheets ofknown type is a low flexibility.

In fact, the starwheel units of known type are capable of making bothlarge-sized stacks, also called “bulk” stacks, for sale to restaurants,cafeterias, communities, or alternatively, smaller stacks, also known as“flat” stacks, for household or personal use. Therefore, in order toswitch from a production to the other it is necessary to use twodifferent machines.

In particular, in case of the “flat” stacks the folded sheets arestacked vertically and released overlapped on the formation table. So,the growth of the stack occurs vertically up to a predetermined height,rather low, and once completed its formation, the table withdraws frombelow of the stack for releasing it on a conveyor belt.

In case, instead, of “bulk” products, the folded sheets are releasedwith the stack that grows horizontally, until it reaches a relevantlength, and brought to the banding in a horizontal direction, as in theabove cited application ITBO2006A000801.

In both cases, several stacks, or packs, are formed, which move from aconfiguration in which they are adjacent creating a line of stacks, to aconfiguration in which all of them are arranged in a row, in such a waythat they can be fed to the banding section at the same time. Suchconfiguration change can be carried out by a pusher that pushes in turnthe stacks of a line on a second conveyor belt, that is parallel to thefirst, for being, then, fed to the banding section, in order to feed thestacks to the banding section it is therefore necessary to providecomplicated conveying devices and proceed at a low speed.

As above disclosed, for feeding the stack to the banding section, whichis arranged downstream of the formation section, it is necessary tooperate a change of direction of the same stack, with the conveyor beltsarranged orthogonally to one another. More precisely, the conveyor beltthat is arranged downstream is adjacent to the conveyor belt that isarranged upstream but leaving a certain unavoidable gap, ordiscontinuity, between them. Therefore during the movement of the stackthrough the gap from a conveyor belt to the other it is possible todamage the product.

SUMMARY OF THE INVENTION

It is therefore a feature of the present invention to provide a machinefor making packages of folded sheets of paper, or similar products,which has a high production rate and has in the meantime a relativelysmall size.

It is also a feature of the present invention to provide a machine formaking packages of folded sheets of paper, or similar products, whichassists handling the stacks formed through the various sections of themachine and, in particular, up to a banding section, avoiding to damagethe product along the path and simplifying structurally the machine.

It is another feature of the present invention to provide a machine formaking packages of folded sheets of paper, or similar products, whichcan work continuously.

It is a further feature of the present invention to provide a machinefor making packages of folded sheets of paper, or similar products,which is highly flexible and, in particular, capable of making bothpackages of large size, i.e. packages of “bulk” type, and smallerpackages, i.e. packages of “flat” type, without substantial structuralchanges to the machine.

These and other objects are accomplished by the machine for makingpackages of folded sheets of paper, or similar material, such asnapkins, or paper tissues, according to the present invention,comprising:

-   -   a feeding means for feeding a plurality of sheets along a        predetermined feeding direction;    -   a starwheel unit mounted rotatable about a rotation axis, said        starwheel unit arranged to receive said plurality of folded        sheets and to put them in turn on a table, in order to form a        stack of folded overlapped sheets according to a first        predetermined stack direction;    -   a transfer means that is arranged to transfer a completed stack        of folded sheets from said table to said conveying means, said        conveying means arranged to convey said stack of folded sheets        along a conveying direction;

whose main feature is that said transfer means comprises a rotationmeans which is arranged to rotate said stack of folded sheets fortransferring said stack from said table to said conveying means, saidrotation means configured to bring the axis of the stack from said firstpredetermined stack direction, when said formed stack is located on saidformation table, to a second predetermined stack direction, when theformed stack is located on the conveying means.

In particular, the first predetermined stack direction can be selectedfrom the group consisting of:

-   -   a substantially horizontal direction;    -   a substantially vertical direction;    -   a direction at a predetermined angle with respect to a        horizontal plane.

Advantageously, the second predetermined stack direction is selectedfrom the group consisting of:

-   -   a substantially vertical direction when the first predetermined        stack direction is substantially horizontal;    -   a substantially horizontal direction when said predetermined        stack direction is substantially vertical.

In particular, the transfer means may comprise, furthermore, atranslation means that is arranged to translate said stack of foldedsheets from said table to said conveying means.

Advantageously, a means is provided for selectively operating saidtranslation means and said rotation means for transferring said stack offolded sheets from said table to said conveying means so that said stackof folded sheets lays on said conveying means with vertical orhorizontal axis.

In particular, during the production of packs, or stacks, of foldedsheets of “flat” type, the means for selectively operating is arrangedto operate the translation means. In this case, the “flat” stack offolded sheets has a substantially vertical axis both when it is locatedon the table and when it is located on the conveying means once it hasbeen transferred to it. Instead, during the production of packs, orstacks, of folded sheets of “bulk” type, the means for selectivelyoperating is arranged to operate the rotation means. In this case, the“bulk” stack of folded sheets turns from a configuration withsubstantially vertical axis when it is arranged on the table to aconfiguration with a substantially horizontal axis when it is located onthe conveying means. In fact, if the “bulk” stack were transported withthe vertical axis free it could fall into pieces and so it would requireto be pressed. This way, then, with a same stacking starwheel system,products of “flat” type and of “bulk” type can be provided. There is,therefore, a high production flexibility between the two types ofproducts, and, in case a flexible banding machines is available, it ispossible to change production very quickly.

Advantageously, downstream of the starwheel unit a banding section isprovided in which to said folded sheet stacks a banding film is applied,for example a film of plastic material, said banding section arrangedalong said conveying direction, such that once arranged on saidconveying means, said folded sheet stacks are carried along a singleconveying direction substantially rectilinear up to entering saidbanding section.

Advantageously, the rotation means is arranged to rotate a stack offolded sheets of an angle set between 80° and 110°, in particular equalto 90°.

In particular, the transfer means can be adapted to transfer the stackof folded sheets from the table to the conveying means through acombination of movements that comprise the above described rotation andat least one translation.

Preferably, the conveying direction is substantially parallel to therotation axis of said starwheel unit.

In particular, the table is substantially “comb-shaped”, which comprisesa plurality of portions alternated to a plurality of empty spaces, saidtransfer means configured pass through said empty spaces for picking upsaid stack of folded sheets from said table and transferring it ontosaid conveying means.

Advantageously, the rotation means comprises a first and a second gripportions that, in use, are arranged at opposite sides with respect tosaid stack, in order to form substantially a gripper, said first andsecond grip portions arranged to move towards/away from each otherbetween a release configuration for said stack of folded sheets and agripping configuration for said stack of folded sheets, and vice-versa.

Preferably, the feeding means is arranged to feed a plurality ofparallel rows of sheets to the starwheel unit, said starwheel unitcomprising a plurality of coaxial starwheel elements each of which isarranged to process a respective row of sheets of said plurality of rowsof sheets arranging in turn said sheets on said table, in order toobtain a respective stack of folded sheets for each row according to anaxis oriented in a predetermined stack direction.

In particular, said plurality of starwheel units are configured to raisestacks of sheets at the same time on respective formation tables.

In this case, the transfer means, and, in particular, the rotationmeans, can transfer at the same time a plurality of folded sheet stacksfrom said formation table to said conveying means. This allows achievinga high production rate without the need of complex technical solutionsfor handling the stacks from the point of releasing the same onto theconveying means up to the banding section. In this case, the first andsecond grip portions of the transfer means has a length suitable forpicking up at a same time all the formed stacks of sheets, for examplevertically, by said starwheel and put them, for example horizontally,onto said conveying means.

In particular, the rotation means comprises a first plurality ofgripping portions and a second plurality of gripping portions, saidfirst and said second plurality of gripping portions arranged in use atopposite sides with respect to said plurality of stacks of sheets andbeing movable towards/away from each other between a grippingconfiguration for said folded sheet stacks and a release configurationfor said folded sheet stacks, and vice-versa.

Advantageously, the conveying means comprises a conveyor belt.

Alternatively, the conveying means comprises a plane fixed support and asmooth surface on which a plurality of handling rods movable withrespect to said plane support are arranged to push slidingly said stackof folded sheets along said conveying direction. It is also possible acombination of the two systems.

In particular, the conveying means has an end arranged at apredetermined distance from the banding section, such that between theconveying means and the banding section a predetermined distance ispresent.

Advantageously, the conveying means is associated with a pushing meansthat is arranged to push said folded sheet stacks to provide apredetermined acceleration to said folded sheet stacks, said push beingapplied by said pushing means when said folded sheet stacks have toreach a correct position directly into the banding machine. Moreprecisely, said push is enough to cause the movement of said stacks ofsheets directly from said conveying means into said banding section.

Preferably, the distance between two successive handling rods is higherthan the width of the stack of folded sheets of a predetermined pitch,so that this pitch is travelled by the transfer means during the timenecessary to the transfer means to reach the path of the conveyingmeans, discharge the stack on the conveying means, and come avoid aninterference with the path of the incoming conveying means. This allowsthe conveying means to work continuously, i.e. to avoid a stepwiseoperation that would be necessary to avoid the interference between theoperation of the transfer means and of the incoming conveying means, andthen to increase further the production rate of the machine.

Advantageously, the table is movable with respect to said starwheelunit, in order to follow the growth of said stack of folded sheets.

An exemplary embodiment of the invention comprises:

-   -   a first starwheel unit arranged to receive from a first feeding        means a first plurality of folded sheets that are carried in        turn along a first feeding direction and to overlap them on a        first table, in order to form a first stack, or series of folded        sheet stacks;    -   a second starwheel unit arranged to receive from a second        feeding means a second plurality of folded sheets that are        carried in turn along a second feeding direction and to overlap        them on a second table, in order to form a second stack of        folded sheets.

In particular, the transfer means is arranged to transfer alternatively,said first and second sheet stacks, or series of folded sheet stacks, onsaid conveying means.

In particular, the first and second starwheel units operate in analternated way, in such a way that, whereas the first starwheel unit iscreating a stack of sheets, the second starwheel unit is not supplied offolded sheets and the stack of folded sheets that has been just formedby the latter is transferred by said transfer means onto said conveyingmeans, and vice-versa.

For example, the first and second starwheel units can be specular withrespect to a midplane of the conveying means.

Advantageously, upstream of said, or each, starwheel unit the followingare provided:

-   -   a longitudinal cutting means, arranged to divide a tape of        paper, or similar material, into a plurality of strips;    -   a folding means that is arranged to fold said strips of paper in        a predetermined configuration, in order to obtain said folded        sheets that are fed to said starwheel unit along said feeding        direction,    -   a transversal cutting means, arranged to cut said strips that        are folded into strip portions into a length corresponding to a        not folded napkin, and    -   a transversal folding means, for folding said strip portions        into napkins.

According to another aspect of the invention a method for making stacksof folded paper sheets, or similar material, such as napkins, or papertissues, comprises the steps of:

-   -   feeding a plurality of folded sheets to a starwheel unit along a        feeding direction;    -   loading orderly said plurality of folded sheets onto a table by        said starwheel unit, in order to form a stack of overlapped        folded sheets;    -   transferring said stack of folded sheets from said table to said        conveying means, which is arranged to convey said stack of        folded sheets along a conveying direction;    -   handling said stack of folded sheets along a conveying        direction;

whose main feature is that said transfer step from said table to saidconveying means is carried out through a rotation of a predeterminedangle of said stack of folded sheets, said rotation means configured tobring the axis of the stack from a first predetermined stack direction,when said formed stack is located on said formation table, to a secondpredetermined stack direction, when said formed stack is located on saidconveying means.

Advantageously, downstream of said starwheel unit a step is provided ofbanding said folded sheet stacks, said step of banding carried out by abanding section by applying a banding film, for example a sheet ofplastic material, about said stack of folded sheets.

In particular, the conveying step of said plurality of folded sheetstacks to said banding section is made along a single conveyingdirection. Therefore, once transferred on said conveying means, thefolded sheet stacks are conveyed to the banding section along a singledirection substantially rectilinear.

Advantageously, the step of transferring comprises the further steps of:

-   -   laterally approaching said stack of folded sheets by a first and        second grip portions movable towards/away from with respect to        each other;    -   approaching further said first and second grip portions to each        other, in order to provide a compression of said stack of folded        sheets;    -   rotating further said first and second grip portions to each        other with said stack of folded sheets still compressed between        them;    -   moving away said first and second grip portions from each other,        in order to release said stack of folded sheets on said        conveying means.

In an exemplary embodiment of the invention the following can beprovided:

-   -   a first starwheel unit arranged to receive a predetermined        number of folded sheets that are carried in turn along a first        feeding direction and to overlap them on a first table, in order        to form a first stack, or series of folded sheet stacks;    -   a second starwheel unit arranged to receive a predetermined        number of folded sheets that are carried in turn along a second        feeding direction and to overlap them on a second table, in        order to form a second stack of folded sheets, in particular        said second starwheel unit being specular to each other, i.e.        arranged in a position symmetric with respect to said first        starwheel unit.

Advantageously between the feeding means and the first and secondstarwheel units a deviation means is arranged to deviate alternativelythe plurality of sheets towards the first, or towards the secondstarwheel unit.

In particular, either of the first and second starwheel units has aplurality of protruding portions, between two following protrudingportions a groove being obtained arranged to receive a sheet of theabove described plurality of sheets.

Advantageously, the first starwheel unit is associated with a firstintroduction means arranged to put a sheet in a groove along a firstintroduction direction and the second starwheel unit is associated witha second introduction means arranged to put a sheet in a groove along asecond introduction direction. In particular, the deviation means isadapted to deviate alternatively said plurality of sheets towards saidfirst and towards said second introduction means.

Advantageously, the deviation means comprises a deviation element havingat least one guide surface arranged alternatively along the firstintroduction direction of the sheets in the first starwheel unit, oralong the second introduction direction of the sheets in the secondstarwheel unit.

In an exemplary embodiment, the deviation means comprises a deviationelement having a first and a second guide surface arranged to bealternatively, and respectively, put along the first introductiondirection of the sheets at the first starwheel unit and along the secondintroduction direction of the sheets at the second starwheel unit.

In particular, an actuating rod can be provided operatively connected tosaid deviation means, said actuating rod arranged to move selectivelysaid deviation means along the first, or the second, introductiondirection respectively.

In an exemplary embodiment, the deviation means comprises at least onedeviation roller equipped with:

-   -   a first holding means for keeping the sheets on a first angular        portion of the surface of said deviation roller, said first        angular portion ending at said first introduction means;    -   a second holding means for keeping said sheets, alternatively to        said first means for keeping, on a second angular portion of the        deviation roller surface, the second angular portion ending at        the second introduction means.

In particular, the transfer means is arranged to transfer alternatively,said first and second sheet stacks, or series of stacks, of foldedsheets on said conveying means.

According to a further aspect of the invention a conveying means isprovided comprising a conveying unit for bringing a plurality of stacks,or packs, of sheets from a stacking section to a banding section, saidconveying unit comprising a pushing means that is arranged to apply,during the movement of said conveying unit, an additional push on saidfolded sheet stacks to provide a predetermined acceleration to saidfolded sheet stacks, said additional push applied by said pushing meanswhen said folded sheet stacks are approaching said banding section. Moreprecisely, the above described additional push is enough to cause themovement of the stack of folded sheets towards said banding section, ina predetermined position of said banding section.

This way, the stack of sheets, which without the pushing means would beleft by the conveying unit on the edge of said banding section, andwould require a further handling for reaching a suitable bandingposition, by the pushing means is brought to a position at which bandingcan start a further handling of the stack of sheets.

In particular, the pushing means applies a push on the folded sheetstacks through a resilient means loaded by a cam means arranged close tosaid banding section. This way, additional drives are not necessary onboard of the conveying means.

BRIEF DESCRIPTION OF THE DRAWINGS

Further characteristic and the advantages of the machine for makingpackages of folded sheets of paper, or similar material, such as tissuepapers, or napkins, according to the invention, will be made clearerwith the following description of an exemplary embodiment thereof,exemplifying but not limitative, with reference to the attacheddrawings, in which like reference characters designate the same orsimilar parts, throughout the figures of which:

FIGS. 1 to 6 diagrammatically show in a elevational side view a possiblesuccession of steps through which the machine operates, according to theinvention, for making packages of folded sheets of paper, or similarmaterial;

FIGS. 7A and 7B diagrammatically show an elevational side view of anexemplary embodiment of the machine shown in FIGS. 1 to 6 in twodifferent operation steps;

FIGS. 8A and 8B diagrammatically show a perspective elevational sideview of a possible exemplary embodiment of the table and of the transfermeans in some operation configurations;

FIG. 9 diagrammatically shows a perspective elevational front view of afurther exemplary embodiment of the machine of FIG. 1;

FIGS. 10 and 11 diagrammatically show a perspective elevational sideview of another exemplary embodiment of the starwheel machine of FIG. 1;

FIG. 12 diagrammatically shows a perspective view of the banding sectionand the loading section of the machine of FIG. 1;

FIGS. 13 to 19 diagrammatically show elevational side views of apossible exemplary embodiment of the conveying means that can beassociated with the machine of FIG. 1 and a pushing system at the exitfrom the conveying unit;

FIGS. 20 and 21 diagrammatically show an elevational side view of twodifferent working configurations of the machine, according to theinvention, for making packages of folded sheets of paper, or similarmaterial;

FIGS. 22 to 27 show front elevational views of some possible exemplaryembodiments of the deviation means adopted in the machine of FIG. 20;

FIG. 28 diagrammatically shows a perspective elevational side view ofthe machine of FIG. 20 equipped with the transfer means for highlightingfurther characteristic structural features.

DESCRIPTION OF A PREFERRED EXEMPLARY EMBODIMENT

With reference to FIG. 1, in a first exemplary embodiment a paperconverting machine 1, according to the invention, comprises a starwheelunit 10 with at least one cylindrical body having a plurality of grooves15, each of which is configured to receive a respective sheet 11 of aplurality of folded sheets 11. More in detail, the above describedplurality of folded sheets 11 are carried in turn, for example betweentwo transmission belts 200 and 201, along a feeding direction 101, forexample a direction substantially tangential to starwheel unit 10. Thelatter rotates about a rotation axis 110, in the figure in acounterclockwise direction, and discharges in turn sheets 11 fromgrooves 15 onto formation table 20, 120. More precisely, the foldedsheets are discharged to achieve a predetermined angular releaseposition, in order to form a stack 50 of folded sheets 11. More indetail, the release of sheets 11 onto table 20, 120 is carried out, forexample, by an extraction rod 18 arranged in the above described angularrelease position.

Upstream of starwheel unit 10 a cutting means can be provided, forexample a cutting roller, not shown in the figures, arranged to dividelongitudinally a sheet, or web, of paper into a predetermined number ofstrips that are then folded according to a predetermined configurationby folding means, also these not shown. The strips of folded paper thusobtained can be then divided into folded strip portions, by atransversal cut and then folded further to form napkins. Such process isof known type and then not shown in the figures.

While on a table 120 a stack being formed is present, on the other table20 the stack already formed 50 is brought towards an outlet zone andthen transferred by a transfer means 60, or 65, to said conveying means30. The latter move stack 50 of folded sheets 11 along a conveyingdirection 102 (FIG. 9). Table 20, or 120, is provided movabletowards/away from starwheel unit 10, in order to follow the growth ofstack 50 of folded sheets and to return eventually to a position ofminimum distance from starwheel unit 10 once rotation means 60 havedrawn stack 50.

Each table, 20, 120, moreover, can work as separator, which separatesthe last sheet 11 of a formed stack 50, from the first sheet 11′ of thefollowing stack 50′. More in detail, the following stack 50′ starts togrow on a table, in the figure table 120, whereas the formed stack 50 istransferred from the other table 20. Alternatively, a separator meanscan be provided, and a single formation table is used, in a way notdescribed in detail since of known type in transfer systems of packagesof folded sheets.

The transfer means can comprise translation means 65, shownadvantageously only in FIG. 1, that is arranged to translate stack 50 offolded sheets from table 20 to conveying means 30, and can comprise arotation means 60 arranged to transfer stack 50 of folded sheets 11 fromtable 20 to conveying means 30 through a rotation (FIGS. 2-6).

Preferably, translation means 65 and rotation means 60 are providedboth. In this case, translation means 65 and rotation means 60 areselectively operated, in particular by a means for selectively operatingnot shown in the figures, for transferring stack 50 from table 20 toconveying means 30.

Rotation means 60 can be adapted to rotate formed stack 50 from aposition in which it has the axis 55 arranged along a substantiallyvertical direction, when it is located on table 20, or 120, to aposition in which the axis 55 is arranged along a substantiallyhorizontal direction, at conveying means 30 (FIGS. 1 to 6).

In an exemplary embodiment diagrammatically shown in FIGS. 7A and 7B,stack 50 grows along a substantially horizontal direction. In this case,table 20, or 120, in order to follow the growth of stack 50, arearranged movable along a horizontal direction 220, in order to containlaterally stack 50 that, during the growth, is supported by a planesupport 255. In this case, rotation means 60 is configured to cause therotation of stack 50 from a position in which the axis 55 is arrangedalong a substantially horizontal direction, when it is located on table20, or 120, to a position in which the axis 55 is arranged along asubstantially vertical direction.

This way, during the production of packs, or stacks, of folded sheets of“flat” type, the translation means 65 is operated, so that the axis 55of the “flat” stack of folded sheets remains substantially vertical alsoonce transferred onto conveying means 30. Instead, during the productionof packs, or stacks, of folded sheets of “bulk” type, the rotation means60 is operated, which brings the “bulk” stack 50 from a configurationwith axis 55 substantially vertical, when it is arranged on table 20, toa configuration with axis 55 substantially horizontal, when it isarranged onto conveying means 30. Therefore, according to the kind ofproduct, “bulk”, or “flat”, the corresponding transfer means isselectively operated.

In case of the “bulk” product, the step of conveying stack 50 from table20 to conveying means 30 is made through a combination of movements,comprising the above described rotation of stack 50 of a predeterminedangle, for example set between about 80° and about 110°, and at leastone translation of rotation means 60. The rotation of the stacks 50 madeby rotation means 60 avoids the stacks 50 to move abruptly alongconveying means 30 with a sudden variation of direction, in particularfor bringing the sheet stacks 50 at a banding section, or packagingsection 80. During the handling of stacks 50 of “bulk” type by conveyingmeans 30, the axis 55 of the stacks 50 remains horizontal and issubstantially orthogonal to conveying direction 102 (FIG. 9).

In a preferred exemplary embodiment, shown in detail in FIGS. 8A and 8B,table 20 has a “comb” shape comprising a plurality of support portions21 alternated to a plurality of empty spaces 22. Therefore, the transfermeans 60, which is also “comb-shaped”, is arranged to match the emptyspaces 22 for picking up stack 50 of folded sheets and transferring itonto conveying means 30.

Rotation means 60 can comprise a first grip portion 61 and a second gripportion 62 that, in use, are arranged at opposite sides with respect tostack 50 and form substantially a gripper. More in detail, the first andsecond grip portions 61 and 62 of the gripper are provided that can bebrought towards/away from each other between a gripping configuration ofstack 50 and a release configuration of stack 50, and vice-versa. Inparticular, in the release configuration the gripping portions 61 andcan approach laterally stack 50 and pass from an external position, inwhich stack 50 is arranged between them (FIG. 8A), and a compressionconfiguration in which the gripping portions 61 and 62 compress stack 50between them for transferring it onto conveying means 30 through theabove described rotation (FIG. 8). After having rotated stack 50, thegripping portions 61 and 62 move away from each other to release stack50 onto conveying means 30 (FIG. 5).

According to an exemplary embodiment of the invention, in case ofpackages, or stacks 50, of “bulk” type, the rotation means 60 transferstack 50 of folded sheets from table 20 to conveying means 30 throughthe following combination of movements:

-   -   laterally approaching the gripping portions 61 and 62 to stack        50 of folded sheets in order to pass from a position external to        stack 50 (dashed line in FIG. 2) to a position in which stack 50        is arranged between them;    -   approaching the first and second grip portions 61 and 62, in        order to provide a compression of stack 50 of folded sheets        between them (full line of FIG. 2);    -   possible translation of the first and second grip portions 61        and 62;    -   rotating the first and second grip portions 61 and 62 with stack        50 of folded sheets still compressed between them, in order put        it over conveying means 30 (FIG. 3);    -   possible translation of the first and second grip portions 61        and 62 closed for placing stack 50 onto conveying means 30;    -   moving away relative to each other of the first and second grip        portions 61 and 62, in order to release stack 50 of folded        sheets onto conveying means 30 (FIG. 4).

In a particular exemplary embodiment of the invention, diagrammaticallyshown in FIG. 9, machine 1 provides a first starwheel unit 10 and asecond starwheel unit 10′. More precisely, the first starwheel unit 10is configured to receive a first plurality of folded sheets 11 that arecarried in turn along a first feeding direction 101 and to overlap themon a first table 20, in order to form a first stack or series of stacks50 of folded sheets, whereas the second starwheel unit 10′ is configuredto receive a second plurality of folded sheets 11′ that are carried inturn along a second feeding direction 101′ and to overlap them on asecond table 20′, in order to form a second stack 50′ of folded sheets.In this case, rotation means 60 is configured to transfer alternativelythe stacks 50 and 50′ of folded sheets from the respective tables 20 and20′ onto conveying means 30. In particular, the first and secondstarwheel units 10 and 10′ operate with a phase shift from each otherfor a predetermined time. Therefore, when stack 50 being formed on table20 has achieved about the half of its final height, the transfer means60 operate the conveying stack 50′ from table 20′ to conveying means 30,and vice-versa. Such technical solution allows, in particular, toincrease remarkably production rate and to limit in the meantime thesize of machine 1. Starwheel units 10 and 10′ are mounted specularly tothe midplane 130 of conveying means 30 and have the respective rotationaxes 110 and 110′ parallel to conveying direction 102.

As shown in the exemplary embodiment of FIGS. 10 and 11, starwheel unit10 can comprise a plurality of starwheel elements, for example fourcoaxial starwheel elements 10 a-10 d. This way, the starwheel machine 10is capable of making at the same time a plurality of stacks of foldedsheets, for example four stacks 50 a-50 d, which grow at the same timeon respective formation tables 20 a-20 d. In this case, rotation means60 rotate at the same time the stacks 50 a-50 d during their transferfrom the respective formation table 20 a-20 d to conveying means 30. InFIGS. 8A and 8B the gripping portions 61 and 62 have been indicated witha same length equal to the width of a package or stack 50. However, thegripping portions 61 and 62 may have a length suitable for picking up ata same time all the sheet stacks 50 a-50 d.

As diagrammatically shown in FIG. 12, downstream of starwheel unit 10 abanding section 80 is provided in which to the stacks 50 of foldedsheets a banding film is applied 81, for example of plastic material,obtaining banded stacks 85.

The banding section 80 is arranged along conveying direction 102 at theend of conveying means 30, which move the stacks 50 from when they aredischarged from the transfer means 60 up to banding section 80. Suchtechnical solution assists remarkably, with respect to the machines ofthe prior art, the operations of handling the stacks 50 through machine1 and to avoid possible damages to the product during the handling bymeans of changes of direction and passage from a conveying system toanother.

Conveying means 30 can comprise a plane support 35, having low frictionsmooth surface, on which the stacks 50 of folded sheets are arranged,and a plurality of handling rods 36 movable with respect to the planesupport 65 for pushing the stacks 50 of folded sheets along the abovedescribed conveying direction 102.

Once reached banding section 80, the sheet stacks 50 are transferredfrom plane support 35 on a platform 82. The latter is provided movablealong a direction substantially orthogonal to conveying direction 102,i.e. along a vertical direction, for example, by at least one actuator83 for bringing stack 50 from a first height to a second height betweenwhich banding film 81 extends. This way, as well known, stack 50, whenpassing from the first to the second height encounters banding film 81that is wound about stack 50 obtaining a banded stack, or package 85,that is transferred to an exit conveyor belt 86. The means for bandingthe packages of folded sheets are indicated diagrammatically, and arewell known to a skilled person, and then a detailed description thereofis not necessary.

In the possible exemplary embodiment of FIGS. 13 to 19 a handling systemis provided formed by handling rods 36 that are integral to a carriage150 moved by a chain mechanism 40 along a loop comprising twosubstantially horizontal portions 40 a and 40 b and two substantiallyvertical portions 40 c and 40 d (FIG. 13). In order to cause a carriage150 to rotate at the connection between a horizontal portion 40 a, or 40b, and the following vertical portion 40 c, or 40 d, the conveying means30 is arranged at a minimum distance from the banding section 80, butsufficient, to make it possible a movement of the rod inbetween.

In particular, conveying means 30 end at a minimum distance 200 from alifting platform 81 of banding section 80 and therefore, betweenconveying means 30 and lifting platform 81 a distance is present 200 ofminimum amplitude, enough to permit the passage of rod 36.

Also here the banding section is described only diagrammatically, sinceit is well known to a skilled person. The lifting platform 82 is movableby an actuator 83, for example a hydraulic actuator, along a direction122 substantially vertical between a first height (FIG. 14) and a secondheight at which a banding film 81 is arranged that is wound about stack50 (FIG. 12).

According to an aspect of the invention, each carriage 150 has a pushingelement 38 integral to handling rod 36. More precisely, at the distance200 the pushing element 38 is adapted to push the sheet stacks 50 toprovide a predetermined acceleration to the stacks 50 same. The abovedescribed push is enough for causing the stacks 50 of folded sheets totravel the distance 200 and, then to pass directly from conveying means30 to platform 81 of banding section 80. More precisely, pusher 38 isadapted to push stack 50 to a position substantially centred withrespect to the banding film 82, in order to ensure that the step ofbanding is made correctly.

Upon reaching a desired position the pushing element 38 translatesforward with respect to carriage 150 operated by a mechanism comprisinga fixed cam means 161 arranged at a predetermined position andcooperating with a mobile cam means 151 integral to carriage 150. Morein detail, mobile cam means 151 is integral to a chain 45 mounted tocarriage 150. Until it reaches the position at which the fixed cam means161 is arranged, chain 45 and mobile cam means 151 to it integral remainstill (FIG. 14). When the mobile cam means 151 reaches an interferencewith fixed cam means 161, chain 45 starts to move (FIG. 15) causing aforward translation of the pushing element and, then, of handling rod 36that pushes stack 50 forward. This produces an acceleration of stack 50suitable for travelling all the distance 200 (FIGS. 16 and 17). During afollowing tilting step of carriage 150 the mobile cam means 151 isdisengaged from the fixed cam means 161 and the pushing element 38, by aspring that is loaded during the movement of the pushing means,withdraws quickly up to returning to the starting position (FIG. 18)whereas the fixed cam means 161 reaches an interference with a mobilecam means 151′ of a successive carriage 150′.

During the handling steps along conveying direction 102, the stacks 50are contained laterally by side containing walls 32 and 33 (FIG. 10).

Alternatively to what above described, conveying means 30 can comprise aconveyor belt, not shown in the figures.

In FIGS. 20 to 28 an exemplary embodiment is diagrammatically shown ofmachine 1 for making packages, or stacks 50 of folded sheets 11 ofpaper, or similar material, such as napkins, or paper tissues. As shownfor example in FIGS. 20 and 21, machine 1 comprises a feeding means 121for feeding a plurality of sheets 11 along a predetermined feedingdirection 101′.

In this case, machine 1 comprises a first starwheel unit 10 that ismounted rotatable about a first rotation axis 110 and a second starwheelunit 10′ mounted rotatable about a second rotation axis 110′ parallel tothe axis 110. In particular, each starwheel is configured to receiveselectively the above described plurality of folded sheets 11 and to putthem in turn onto a first table 20 and a second table 20′, respectively.This way, the first and second starwheel units 10 and 10′ formrespectively a first and a second stack of folded overlapped sheets 50,and 50′ (FIGS. 20 and 21).

More in detail, between the feeding means 121 and starwheel units 10 and10′ a deviation means 250 is arranged to deviate alternatively the abovedescribed plurality of sheets 11 towards first starwheel 10 (FIG. 20),or towards second starwheel 10′ (FIG. 21). Like first starwheel unit 10,also second starwheel 10′ has a plurality of grooves 15′, each of whichis arranged to receive a sheet 11 of the above described plurality ofsheets.

Each starwheel unit 10, or 10′, is associated with respectiveintroduction means 210, or 210′, for example two conveyor belts 200 and201, or 200′ and 201′, arranged to put a sheet 11 in a respective groove15, or 15′. More precisely, the introduction means 200 supply sheets 11to the starwheel 10 along a first introduction direction 101, whereasthe introduction means 210′ supply sheets 11 to the starwheel 10′ alonga second introduction direction 101′.

As diagrammatically shown in FIGS. 22 to 25, the deviation means 250 cancomprise a deviation element 250 having at least one guide surface 251arranged alternatively along the first introduction direction 101 forfeeding sheets 11 towards first starwheel unit 10 (FIG. 22), or alongthe second introduction direction 101′ for feeding sheets 11 towardssecond starwheel unit 10′ (FIG. 23). For example, the deviation element250 can be mounted rotatable about a rotation axis 255.

In a possible exemplary embodiment diagrammatically shown in FIGS. 24and 25, the deviation means 250 can comprise a deviation element 250′,for example substantially wedge shaped, having a first guide surface 251a and of a second guide surface 251 b which can be alternatively, andrespectively, put along the first introduction direction 101 for feedingstarwheel 10 (FIG. 24) and along second introduction direction 101′ forfeeding starwheel 10′ (FIG. 25).

In particular, an actuating rod is provided 70 operatively connected toone end to deviation element 250′ and at the other end to an cam 75.Therefore, the actuating rod 70 is arranged between an advanced positionin which the deviation element 250′ has the guide surface 251 a arrangedalong the first introduction direction 101 and therefore sheets 11 arefed to the first starwheel unit 10 (FIG. 24), and a withdrawn position,in which the deviation element 250′ moves with the guide surface 251 balong introduction direction 101′ and therefore sheets 11 are fed tostarwheel unit 10′ (FIG. 25). In particular, for bringing the deviationelement 250′ from the actual position of FIG. 24 to the position of FIG.25, or vice-versa, handling rod 70 translates, thus withdrawing, oradvancing, and causing the rotation of deviation element 250′ about arotation axis 255′ in a rotation direction, or in the oppositedirection.

In a further exemplary embodiment diagrammatically shown in FIGS. 26 and27, the deviation means 250 comprises at least one deviation roller 25having a first holding means, for example a suction means not shown inthe figure, and for example as described in WO2011015893 in the name ofthe same applicant, for keeping sheets 11 at a first angular portion 26of its surface, i.e. that correspond to centre angle α. More in detail,the first angular portion 26 ends at the first introduction means 210comprises for example a second deviation roller 35, which also has aholding means, for example means suction, and arranged to transfersheets 11 from the deviation roller 25 towards the introductiondirection 101 to starwheel 10.

The deviation roller 25 also comprises a second holding means, also notshown in the figures, for holding, alternatively to the first holdingmeans, sheets 11 on a second angular portion 27 of the surface of saiddeviation roller 25, i.e. that correspond to centre angle β. More indetail, the second angular portion 27 ends at second introduction means210′ comprising a third deviation roller 36, which also has a holdingmeans, for example a suction means, and arranged lead sheets 11 from thedeviation roller 25 towards introduction direction 101′ of the starwheel10′. Other configurations are possible for deviating the sheets by meansof vacuum transfer rollers. For example conveyor belts 200 and 200′a cancontact directly the vacuum roller 11.

Alternatively, the introduction means 200 and 200′ can be movable, inparticular alternatively, towards/away from the deviation roller fortransferring sheets 11 from the deviation roller 25 to starwheel 10, or10′.

As diagrammatically shown in FIG. 28, furthermore, a conveying means isprovided 30 arranged to bring the stacks 50 along a conveying direction105 substantially parallel to rotation axes 110 and 110′ of starwheelunits 10 and 10′. In particular, the first and second starwheel units 10and 10′ are arranged in symmetrical positions with respect to an axis ofsymmetry 130 orthogonal to conveying direction 105. In this way the samerotation means 60 can be used for transferring the stacks 50 and 50′from the respective formation tables 20 and 20′ onto conveying means 30.

The foregoing description of specific exemplary embodiments will sofully reveal the invention according to the conceptual point of view, sothat others, by applying current knowledge, will be able to modifyand/or adapt in various applications the specific exemplary embodimentswithout further research and without parting from the invention, and,then it is meant that such adaptations and modifications will have to beconsidered as equivalent to the specific embodiments. The means and thematerials to realise the different functions described herein could havea different nature without, for this reason, departing from the field ofthe invention. It is to be understood that the phraseology orterminology that is employed herein is for the purpose of descriptionand not of limitation.

1. Machine for making stacks of folded paper sheets, or similarmaterial, such as napkins, or paper tissues, comprising: a feeding meansfor feeding a plurality of sheets along a predetermined feedingdirection; a starwheel unit mounted rotatable about a rotation axis,said starwheel unit arranged to receive said plurality of folded sheetsand to put them in turn on a table, in order to form a stack of foldedoverlapped sheets according to a first predetermined stack direction; atransfer means that is arranged to transfer a completed stack of foldedsheets from said table to said conveying means, said conveying meansarranged to convey said stack of folded sheets along a conveyingdirection; characterised in that said transfer means comprises arotation means which is arranged to rotate said stack of folded sheetsfor transferring said stack from said table to said conveying means,said rotation means configured to bring the axis of the stack from saidfirst predetermined stack direction, when said formed stack is locatedon said formation table, to a second predetermined stack direction, whensaid formed stack is located on said conveying means.
 2. Machine,according to claim 1, wherein said first predetermined stack directionis selected from the group consisting of: a substantially horizontaldirection; a substantially vertical direction; a direction at apredetermined angle with respect to a horizontal plane.
 3. Machine,according to claim 1, wherein said second predetermined stack directionis selected from the group consisting of: a substantially verticaldirection when said predetermined stack direction is substantiallyhorizontal; a substantially horizontal direction when said predeterminedstack direction is substantially vertical.
 4. Machine, according toclaim 1, wherein said transfer means comprises, furthermore, atranslation means that is arranged to translate said stack of foldedsheets from said table to said conveying means, and a means is providedfor selectively operating said translation means and said rotation meansfor transferring said stack of folded sheets from said table to saidconveying means.
 5. Machine, according to claim 4, wherein during theproduction of packs, or stacks, of folded sheets of “flat” type saidmeans for selectively operating operate said translation means such thata “flat” stack of folded sheets remains substantially with vertical axisboth on the table and on said conveying means once transferred. 6.Machine, according to claim 4, wherein during the production of packs,or stacks, of folded sheets of “bulk” type said means for selectivelyoperating is arranged to operate said rotation means for bringing said“bulk” stack of folded sheets from a configuration with substantiallyvertical axis when it is arranged on said table, to a configuration withaxis substantially horizontal when it is located on the conveying means.7. Machine, according to claim 1, wherein downstream of said starwheelunit a banding section is provided in which to said stack of foldedsheets a banding film is applied, said banding section arranged alongsaid conveying direction, such that once arranged on said conveyingmeans, said stack of folded sheets moves along a single conveyingdirection substantially rectilinear up to entering said banding section,in particular said conveying direction is substantially parallel to saidrotation axis of said starwheel unit.
 8. Machine, according to claim 1,wherein said transfer means is arranged to transfer said stack of foldedsheets from said table to said conveying means through a combination ofmovements that comprise a rotation of the stack of folded sheets for anangle set between 80° and 110°, in particular 90°.
 9. Machine, accordingto claim 1, wherein said table has is substantially “comb”-shaped,comprising a plurality of portions alternated to a plurality of emptyspaces, said transfer means configured to be put at said empty spacesfor picking up said stack of folded sheets from said table andtransferring it onto said conveying means, in particular said rotationmeans comprises a first and a second grip portions that can be broughttowards/away from each other between a gripping configuration of saidfolded sheet stacks and a release configuration of said folded sheetstacks, and vice-versa.
 10. Machine, according to claim 1, wherein saidfeeding means is arranged to feed a plurality of parallel rows of sheetsto said starwheel unit, said starwheel unit comprising a plurality ofcoaxial starwheel elements each arranged to process a respective row ofsheets of said plurality of rows of sheets arranging in turn said sheetson said table, in order to make a respective stack of folded sheets foreach row according to an axis oriented in a predetermined stackdirection.
 11. Machine, according to claim 10, wherein said rotationmeans is adapted to transfer at the same time said plurality of foldedsheet stacks from said formation table to said conveying means. 12.Machine, according to claim 1, wherein said conveying means has an endclose to a banding section, said conveying means being associated with apushing means that is arranged to push said folded sheet stacks toprovide a predetermined acceleration to said folded sheet stacks, saidpushing means configured to apply said push in said conveying directionfor displacing said stack directly to said banding station.
 13. Machine,according to claim 12, wherein said conveying means comprises a planesupport on which a plurality of handling rods, movable with respect tosaid plane support, move said stack of folded sheets along saidconveying direction, in particular the distance between two successivehandling rods being higher than the width of said stack of foldedsheets, in order to cause the conveying means to work continuously. 14.Machine, according to claim 1, comprising: a first starwheel unitarranged to receive from a first feeding means a first plurality offolded sheets that are carried in turn along a first feeding direction,and to overlap them on a first table, in order to form a first stack, orseries of folded sheet stacks; a second starwheel unit arranged toreceive from a second feeding means a second plurality of folded sheetsthat are carried in turn along a second feeding direction and to overlapthem on a second table, in order to form a second stack of foldedsheets, in particular said first and said second starwheel unitsconfigured to work in an alternated way, in such a way that, while saidfirst starwheel unit is creating a stack of sheets, said secondstarwheel unit is not supplied of folded sheets and the stack of foldedsheets that has been just formed by the latter is transferred by saidtransfer means onto said conveying means, and vice-versa.
 15. Machine,according to claim 1, comprising: a first starwheel unit mountedrotatable about a first rotation axis, said first starwheel unitarranged to receive said plurality of folded sheets and to put them inturn on a first table, in order to provide a first stack of overlappedfolded sheets; a second starwheel unit mounted rotatable about a secondrotation axis parallel to said first rotation axis, said secondstarwheel unit arranged to receive said plurality of folded sheets andto put them in turn on a second table, in order to provide a secondstack of overlapped folded sheets; wherein each starwheel unit amongsaid first and said second starwheel unit has a plurality of protrudingportions, between two following protruding portions a groove beingobtained arranged to receive a sheet of said plurality of sheets; andwherein between said feeding means and said first and second starwheelunits a deviation means is arranged to deviate alternatively saidplurality of sheets towards said first, or said second starwheel unit.16. Machine, according to claim 15, wherein said first starwheel unit isassociated with a first introduction means, said first introductionmeans arranged to put a sheet in a groove along a first introductiondirection and said second starwheel unit is associated with a secondintroduction means, said second introduction means arranged to put asheet in a groove along a second introduction direction, said deviationmeans arranged to deviate alternatively said plurality of sheets towardssaid first and towards said second introduction means.
 17. Machine,according to claim 15, wherein said deviation means comprises adeviation element having at least one guide surface arrangedalternatively along said first introduction direction of said sheets insaid first starwheel unit, or along said second introduction directionof said sheets in said second starwheel unit.
 18. Machine, according toclaim 15, wherein said deviation means comprises a deviation elementhaving a first and a second guide surface arranged to be alternatively,and respectively, put along said first introduction direction of saidsheets into said first starwheel unit and along said second introductiondirection of said sheets into said second starwheel unit.
 19. Machine,according to claim 15 wherein an actuating rod is provided operativelyconnected to said deviation means, said actuating rod arranged to moveselectively said deviation means along said first, or said second,introduction direction respectively.
 20. Machine, according to claim 15,wherein said deviation means comprises at least one deviation rollerequipped with: a first holding means for keeping said sheets on a firstangular portion of the surface of said deviation roller, said firstangular portion ending at said first introduction means; a secondholding means for keeping said sheets, alternatively to said first meansfor keeping, on a second angular portion of the surface of saiddeviation roller, said second angular portion ending at said secondintroduction means.
 21. Method for making stacks of folded paper sheets,or similar material, such as napkins, or paper tissues, comprising thesteps of: feeding a plurality of folded sheets to a starwheel unit alonga feeding direction; releasing said plurality of folded sheets onto atable by said starwheel unit, in order to form a stack of overlappedfolded sheets; transferring said stack of folded sheets from said tableto said conveying means, which is arranged to convey said stack offolded sheets along a conveying direction; handling said stack of foldedsheets along a conveying direction; characterised in that said transferstep from said table to said conveying means is carried out through arotation of a predetermined angle of said stack of folded sheets, saidrotation configured to bring the axis of the stack from a firstpredetermined stack direction, when said formed stack is located on saidformation table, to a second predetermined stack direction, when saidformed stack is located on said conveying means.
 22. A conveying unitfor bringing a plurality of stacks, or packs, of sheets from a stackingsection to a banding section characterised in that said conveying unitcomprises a pushing means that is arranged to apply, during the movementof said conveying unit, an additional push on said folded sheet stacksto provide a predetermined acceleration to said folded sheet stacks,said additional push applied by said pushing means when said foldedsheet stacks are approaching said banding section.